life11e_ch28

Fruits aid angiosperm seed dispersal

Fruits often aid in seed dispersal. Fruits may attach to or be eaten by an animal. The animal is then likely to move, after which the seeds may fall off or be defecated. Fruits are not necessarily fleshy. Fruits can also be hard and woody, or small and have modified structures that allow the seeds to be dispersed by wind or water (Figure 28.17).

Figure 28.17 Fruits Come in Many Forms (A) The single seeds inside the simple fruits of Bing cherries are dispersed by animals. (B) Each seed of the horse chestnut is covered by a hard, woody fruit that allows it to survive drought. Although such fruits are commonly called “nuts,” this is a culinary rather than a biological term. (C) The highly reduced simple fruits of dandelions are dispersed by wind. (D) A multiple fruit, the pineapple (Ananas comosu), has become one of the most economically significant fruit crops of the tropics. (E) An aggregate fruit (blackberry). (F) An accessory fruit (pear).

Question

Q: The large incisors of rodents help these animals penetrate the shells of woody nuts, which they consume as food. But unlike many animals that eat fruits without digesting the seeds, rodents destroy the seeds when they eat them. So how do rodents aid in dispersing the seeds of nut-bearing plants?

Although rodents destroy the seeds of nut-bearing plants when they eat them, these plants produce far more nuts than rodents can immediately eat. Rodents gather extra nuts and stash them for later consumption in or around their nests, often burying them in soil in the process. Many of these extra nuts then germinate before they are consumed by the rodents.

A fruit may consist of only the mature ovary and its seeds, or it may include other parts of the flower or structures associated with it. A simple fruit is one that develops from a single carpel or several fused carpels, such as a plum or cherry. A raspberry is an example of an aggregate fruit—one that develops from several separate carpels of a single flower. Pineapples and figs are examples of multiple fruits, formed from a cluster of flowers (an inflorescence). Fruits derived from parts in addition to the carpel and seeds are called accessory fruits—examples are apples, pears, and strawberries.

Media Clip 28.3 Flower and Fruit Formation